Electrolytic methods and apparatus for production of metal hydroxides



P. S. ROLLER ELECTROLYTIC METHODS AND APPARATUS FOR Jan. 26, 1954 PRODUCTION OF METAL HYDROXIDES Filed March 13, 1948 3 Sheets-Sheet 1 NVENTOR aLLEK Wm/ ...r

Jan. 26, 1954 P. s. ROLLDER 2,667,454

ELECTROLYTIC METHODS AN ABPARATUS FOR PRODUCTION OF METAL HYDROXIDES Filed March 13, 1948 '3 Shets-Sh'eet 2 P. v E I '/&0

INVENTOR. fl/UL 'lF 6 Jan. 26, 1954 P. s. ROLLER 2,667,454 ELECTROLYTIC METHODS AND APPARATUS FOR PRODUCTION OF METAL HYDROXIDES Filed March 13, 1948 3 Sheets-Sheet 3 Q o 0 0 0 0 0 0 0 0 o 0 0 0 0 0 0 0 6 0 0 O 0 0 a 0 0 0 0 I! I .500 20/ I A B c 1) ta -13 s O INVENTOR. E4 11. f. 161.45

Patented Jan. 26, 1954 UNITED STATES PATENT OFFICE ELECTROLYTIC METHODS AND APPARA- TUS FOR PRODUCTION OF METAL HY DROXIDES 17 Claims. 1

The present invention relates to the electrolytic production of water-insoluble metal hydroxides, and although not limited thereto, it will be particularly described inits application to the electrolytic production of aluminum hydroxide. A continuation-in-part of this application is my co-pending application, Serial Number 99,802, disclosing a method of utilizing the subject matter of the present application in liquid purification.

It is among the objects of the present invention to provide a novel, elfective method of producing suspensions of metal hydroxides without need of precipitation of such hydroxides from solution by addition of alkalies, and without their contamination by absorbable ions.

Another object is to provide a novel, low cost, electrolytic procedure for producing metal hydroxides from sub-divided metal such as turnings, borings, shot, cuttings, chips, granulation or other particles, and without the need for using relatively expensive rolled sheets or plates.

Another object is to provide a novel electrolytic procedure which Will provide a high output of metal hydroxide at a low power requirement.

Still another object is to provide a novel water purification and clarification procedure which is based upon the production of aluminum hydroxide or ferric hydroxide from their respective turnings, cuttings, borings, granulations, and the like.

Still further objects and advantages will appear in the more detailed description set forth below, it being understood, however, that this more detailed description is given by way of illustration and explanation only and not by way of limitation, since various changes therein may be made by those skilled in the art without (16- parting from the scope and spirit of the present invention.

In accomplishing the above objects, it has been found most satisfactory to confine a mass of subdivided metal, to be converted into metal hydroxide or hydrate, into beds which are separated by diaphragms. A battery of beds is thus formed, and these are maintained under substantial compression between end-plates or walls. A constant direction direct current, or periodically reversing direct current, is passed through the beds while passing water therethrough, said water containing a salt or other electrolyte or ionized compound, either present naturally or added artificially. The diaphragms may be bordered by a framework or enclosure which contains the bed oi metal, thereby forming a cell.

The output of hydroxide in the cells will be taken up by the stream of water. In the course of time, the concentration of hydroxide in the water may be greatly reduced. This is due to an increasing retention of the generated hydroxide by the metal particles within the cells. The retained metal hydroxide may be eiiectively released by subjecting the cells to a flushing action during continuous production of metalhydroxide in the battery, in the manner as hereinafter described. Various flushing procedures including recirculation of the efiluent water, increasing the rate of flow, interrupting or reversing the flow, and commingling of air or gas in the water may be employed. It is also possible to use combination of recirculation and commingling of air or gas.

The diaphragms should be impervious to the metal particles, but permeable to water and dissolved electrolytes, permitting passage of the current from cell to cell. Depending upon the direction of the current, one cell may serve as anode and an adjacent cell of the same metal as cathode, or the same cell may serve both as anode and cathode.

The metal to be converted to hydroxide may for example consist of aluminum, magnesium, copper, iron or nickel, in the form of clean turnings, borings, chips, cuttings, granules and the like. The diaphragm is preferably non-rigid, and desirably thin and pliant, so that the various metal particles may be well compacted against the surface of the diaphragm. Before placing in a cell, the particles are preferably stamped or pounded and somewhat flattened, and may be screened to a desired size, cleaned by washing, and dried. A compression of the metal particles in the cell against the diaphragms is maintained, during consumption of the metal under the action of the current and electrolyte by a follower endplate and a pressure screw or toggle joint when the diaphragms are in a vertical plane, or by a heavy weight when the diaphra ms are in a hori-. zontal plane. The pressure-plate, or the weight, moves as the battery decreases indepth due to the consumption of metal, and the desired compression is thus maintained.

The water which may contain the normal amount of dissolved salts, or added electrolyte, may be caused to pass acrossthe diaphragms, parallel to the direction of the current flow. I have found that an efiicient result may be obtained by flowing the water in the cells parallel to the diaphragms, and tranversely to the direction of the current flow.

The cells may be connected electrically in par-' 3 allel, applying a current lead to each cell servillg alternately as anode or cathode. The cells may also be desirably connected in series fashion, each cell serving both as anode and cathode, with current leads applied only to the terminal cells of the battery.

Essentially, the apparatus consists of an internally non-conducting horizontal or vertical tank containing a mass of compacted sub-divided metal separated into a plurality of beds of metal by electrically non-conducting vertically or horizontally positioned water-pervious diaphragms. Electric current is caused to flow through the metallic circuit in the beds and electrolyte in the diaphragms. The diaphragms are arranged to be movable to keep the metal particles well compacted under pressure, as the metal is :consumed and converted into hydroxide. An enclosure around the edges of the diaphragms may be added to form separate cells. The enclosure will confine the sub-divided metal to the bed, while water freely flows through the bed. In addition to the inlet for the normal flow of water, auxiliary inlets are provided for recirculating efiiuent back .to the cells during passage of the electric current.

The drawings serve diagrammatically to illustrate the procedures and constructions which may be employed to accomplish the invention. In the drawings:

Fig. 1 is a diagrammatic vertical side sectional view showing illustratively one form of apparatus according to the present invention.

Fig. 2 is a diagrammatic vertical side sectional View of an alternative arrangement.

Fig. 3 is a diagrammatic vertical side sectional view of a further alternative arrangement.

Fig. 4 is a diagrammatic vertical side sectional view of still another alternative arrangement.

Fig. 5 is a diagrammatic vertical side sectional View of yet another alternative arrangement.

Fig. 6 is an isometric view of a preferred form of cell construction.

Fig. '7 is a diagrammatic vertical side view of a further alternative arrangement employing a preferred form of cell construction.

Fig. 8 is a vertical transverse sectional view upon the line 8-8 of Fig. '7.

In Fig. 1, the battery of cells A, B, C and D, each containing compacted and compressed subdivided metal, is formed in thechamber or tank I. The tank l is of such material, or so coated, as to be electrically non-conducting on its interior surface.

Four cells A, B, C and D of Fig. 1 are filled with sub-divided metal material. The anode cells A and C are connected to a positive source of potential, and the cathode cells B and D connected to a negative source of potential. Each cell is defined by a diaphragm 2, two oppositely disposed narrow top and bottom end-pieces 3, and two oppositely disposed narrow side-pieces forming the lateral edges of each of the battery cells A to E. Thediaphragms 2, which are nonducting, are movable in response to mechanical thrust or pressure. The end-pieces 3 and side-pieces 4 of the cells A to D are of a flexible contractile material, preferably thin rubber, and offer practically no restraint to a movement of the diaphragms 2.

End-plates 9 of non-conducting material or coated to be non-conducting, press the metal particles in the cells A to D tightly against the diaphragms 2 through the respective thrust members or screws Ill. The members {0; which pass 4 through insulating stuffing boxes H, are turned by the hand wheels 52, to adjust the compression of the beds of metal in the cells A to D.

Inlets 5 admit water containing its normal content of mineral salts, or with added electrolyte such as sodium chloride or sodium acetate, to the cathode cells B and D. Inlets 5 pass through the wall of tank I and terminate in end-pieces 3. The inlet diameters are small relative to the width of the cells. The inlets 5 are desirably flexible and extra long so as to remain joined with their cells during any displacement motion of the cell walls 2. The header 6 feeds inlets $5.. The outlets ll from the anode cells lead to the conduit 8. Inlets and outlets 5 and l are of non-conducting material or are suitably insulated.

In Fig. ,1, the water passes from inlets 5 into the cathode cells B and D across the separating diaphragms 2 into the adjacent anode cells A and C and thence out through outlets 1. The end-pieces 3 and side-pieces 4 prevent particles of metal from bridging over and short-circuiting the cell during flow of the water. The inlets and outlets 5 and 1 may be protected against entry of metal particles by insulating gauze or a perforated plate. The metal hydroxide is generated in the anode cells, and flows out with the Water through outlets I. The same metal is used in all the cells. By periodically reversing the current and the direction of flow of water, the metal of all the cells may be equally consumed.

As the sub-divided metal anodes are consumed during continued passage of the current, the resultant slack in the cells A to D is taken up, and pressure of the metal particles against the diaphragms 2 is maintained, by adjustment of the thrust members ii).

The diaphragms 2 are impervious to the metal particles but pervious to the water. Thin porous pliant materials are most desirable. Highly porous cloth diaphragms have been found to be highly serviceable, permitting a large current. Thus, in one test, a thin perforated Bakelite disk as a diaphragm gave a current of 0.08 amp/sq. ft. volt, while a canvas diaphragm gave 0.32 amp. The cloth constituting the diaphragm may be of canvas, duck, sailcloth, Oxford cloth, or woven of glass or synthetic fibre.

The thinner, more porous and more pliant the material the lower the resistance to the current. With sailcloth, which was somewhat thinner, more porous and more pliant than canvas, a current of 0.6% amp. was obtained, as against only 0.32 amp. for the canvas. The sailcloth was quite resistant to piercing by the metal particles.

It is desirable to stamp and partially flatten the metal turnings or borings before placing them into the cells, so as to obtain good compacting and a high density of fill in the cell. It is desirable also to wash the stamped metal with a detergent solution, and to dry it before placing it into the cells.

I have found that they yield of metal hydroxide decreases with time. I have, however, been able to obtain a consistently high yield of metal hydroxide by periodically recirculating efiiuent back to the anode cells.

An embodiment involving an eiiluent recirculating arrangement is shown in Fig. 2. In this figure, the anode cells and C are provided with recirculation inlets 13, which are opposite to the anode outlets T. The inlets 13 are joined to a, header it. Recirculated efiuent, entering 5. the anode cells A and C through inlets l3, unites with the water from cathode inlets after it has traversed the diaphragms 2, and the combined volume of water leaves the anode cells A and C in combination by outlet pipes I.

In order to increase concentration of the suspension of metal hydroxide, part of effluent may be recirculated. In Fig. 2, the inlet side of the header It connects to recirculating pump [5, while the other side of pump is connected by conduit I6 to outlet header 8. A portion of the flow through outlet 8 is recirculated by conduit I6 and pump l5 to the battery through inlet conduits Id and I3.

During electrolysis, the anode compartments A and C tend to become acid and the cathode compartment alkaline, giving rise to a concentration polarization and resultant increased power requirement. By passing the electrolyte through or across the diaphragm and thus mixing the cell solutions, this effect is largely overcome. Another result of passing across the diaphragm is to keep the pores of the diaphragm open against the plugging tendency of anode-generated metal hydroxide.

A disadvantage on the other hand of passing the aqueous electrolyte solution across the diaphragm is the hydraulic resistance to flow. I have found that a good result is obtained, in the instance of an appreciable flow of electrolyte, if it is passed parallel to the diaphragm, instead of across it. Since the liquid will only stay in the cells a short time, appreciable concentration gradients from cell to cell will not develop. In the instance of recirculation, the solutions are mixed outside of the cells. Turbulence in the cell compartments incidental to recirculation is effective in maintaining the diaphragms clean. The avoidance of flow across the diaphragms is particularly useful in the instance of a turbid solution.

In Fig. 3 the water containing electrolyte flows parallel to the diaphragms 2 and transverse to the current in each of the cells A to D. The solution enters each cell individually through inlets i'l, each of which has its corresponding outlet 88. The inlets ll connect to a header i9, and. the outlets i8 connect to a header 2D. Recirculation of part of the effluent for increasing concentration of dispersed metal hydroxide is effected by pump 2 l, connected to outlet header by conduit 22, and connected to inlet header It by conduit 23.

In Fig. 3 each cell is similar in function to each other cell. This arrangement is particularly desirable where the cells are electrically connected in series instead of in parallel, as in Figs. 1 and 2. The series connection is desirable in case of substantial shifting of the cells during consumption of the metal, which causes difficulty of maintaining electrical contact with each cell. In the series connection only the terminal cells are connected to a source of potential.

In Fig. 3 the non-conducting end-plates 24 have metal prick-points 25 which pierce the adjacent diaphragms 2 thereby making contact with the metal in the end cells A and D. The prick-points 25 may receive their potential through electrical connections to thrust members 25.

In the series connection each cell serves both as an anode and a cathode, the respective p0- larities being on opposite sides of each cell adiacent to the respective diaphragms. The series arrangement permits a high voltage, low amperage current.

The increase in concentration of dispersed metal hydroxide by recirculation of the battery effluent is aided by periodically interrupting the flow of water, or by reversing the flow of battery effluent, or the latter two procedures may be employed in lieu of recirculation.

I have found that a particularly effective and convenient method of obtaining metal hydroxide is to commingle air with the water. This method is so effective that employment of recirculation for obtaining metal hydroxide can be generally dispensed with. Recirculation, as herein described, is necessary when a high concentration of metal hydroxide in the solution is required. In this instance the recirculation is employed not for flushing but to build up the solids concentration of dispersed metal hydroxide in the water.

In the normal operation of a metal hydroxide producing battery, the effluent water as it issues from the battery has a certain content of the metal hydroxide which is generated at the electrodes. This metal hydroxide content is limited, and the concentration continues to decrease to small values after a certain interval of operation of the battery. Now, if the fresh water passes through the battery, by way of conduits 8 and 5 oi. Fig. 2 or conduits 20 and IQ of Fig. 3, at the same constant rate, with a portion of the efiluent containing the freshly generated metal hydroxide continuously recirculated, by pumps l5 and 21, by way of conduits i3, i4 and IS in Fig. 2, or conduits 23 and 22 shown in Fig. 3, respectively, then the content of aluminum hydroxide in the eiiluent becomes greater and finally constant, and clearly observable as a higher yield in the efliuent than when there is no continuous recirculation at the same constant rate of flow of fresh water. As illustrated in the drawings and herein stated in the specification, the necessary and preferred process, is with recirculation of the eiiluent containing freshly generated metal hydroxide. This eilluent is pumped back into the battery before or without any separation of its metal hydroxide content. When so recirculated the metal hydroxide is an added booster stream of uncoagulated, dispersed metal hydroxide which increases the flow rate, and is thus believed to overcome certain forces, mostly electrostatic arising from the action of the electrodes. These forces act to hold up and retain in the form of interposed masses the generated metal hydroxide. The recirculation of the effluent containing the dispersed freshly generated metal hydroxide imparts an inner velocity and force that is able to overcome the interelectrode forces, and displaces the held masses of metal hydroxide into the flowing stream and thus into the effluent in a dispersed and unco agulated state. The yield of the dispersed metal hydroxide in the recirculated effluent, aside from any additional reaction of electrolysis which may occur, is thus observably higher as a uniformly colored and relatively thicker and more dense fluid than it is in the effluent in the absence of recirculation.

In the embodiment of Fig. 4, commingled air and water is used for flushing. There is provided a header 29- for the inlets '21 and an other header 30 for the outlets 28. Air conveyance conduit 3| joins the solution inlet header 29 at junction 32. The air may be pumped through conduit 3| into conduit 29; on the other hand, an aspirator may be located at junction acetate 32,. for drawing air from conduit 3!. Both-procedures if desired, may be combined. In the. former instance, conduit 35 is connected to an air pump, and in the latter instance the conduit 3! is connected to the atmosphere.

Conduit 35 leads to an air vent chamber 33, the excess air escaping through valve 3 3 located at the top of chamber The hydroxide-laden water, substantially freed of its commingled air, leaves by outlet 35.

I'he ratio by volume of comzningled air to water may vary within wide limits between about 0.1 and 30. At a moderate rate of water flow, a good result in the instance of aluminum was consistently obtained with a ratio of about 3 to 6.,

The use of commingled air and water apparently yields a better settling floc of aluminum hydroxide than when water alone is used for producing a metal hydroxide.

The air may be commingled with the infiowing water continuously, or the comlningling of the air may be periodically interrupted, and auxiliary water be ccmbined for producing a metal hydroxide dispersion or the air may be combined with recirculation of the efiluent. For instance, effluent from pipe 35 in Fig. 4 may be recirculated to pipe giving rise to a mixed recirculated effluent and air causing production of a concentrated solution of dispersed metal hydroxide.

In the instance of a large battery of narrow cells, the depth of the battery decreases as the metal is consumed if the pressure is maintained by thrust screws ill or 2%. There is then some difficulty in maintaining continuous communication between the cells and the respective inlets and the outle Us.

To overcome difficulty, in Fig. 5 an inlet to cells A, B, C, D, and E is provided by the punched screen 35, and an outlet is provided by the punched screen ifa'i. The screens are of non-conducting material, such as hard rubber or Bakelite, or of a coated material. The end-pieces for each of the cells A, B, C, D, and E differ from the end-pieces 3 of Fig. 1, in that they are perforated, the perforation being fine enough to permit passage of turbid water, but not the metal particles in cells. The side-pieces IE4 are the same as the side-nieces i of Fig. 1 Water passes through the inlet I99 into the header space lie, through punched screen the end-strips H33, the cells A to E, the opposite end-strips m3, the punched screen lfl'i, t.e header space ill, and through outlet As the metal is consumed, the battery is contracted to maintain the cell compression by the end-plates i353 actuated by thrust screws 199. At the same time valves iii; are moved together by screw members iii so that the water must flow through the cells A, B, C, D, and E before reaching outlet Valves We are preferably of a thick, rubber material to effect a good seal against plate Ebb and the bottom wall of tank its. in general, the valves Iii} are positioned at the end-p1ates i853.

It is possible to operate with only one pressure end-plate valve, using the end wall of tank ilf; the second pressure plate and valve. However, by the use of two pressure plates and valves, the central cell of the battery remains in place while the battery depth decreases. An electrode its may be conveniently attached to the center cell so as to split the potential across the battery and thus reduce the magnitude: of: the applied. potential if desired. Frictionof the edges of the cells against the parti tionor tank walls and internal friction results in a pressure v gradient and unequal distribution of pressure among the cells. The use of bilateral rather than. unilateral dynamic pressure effects amore even distribution of the pressure. These advantages must be balanced against the disadvantages of a greater initial cost of two pressure end-plates and valve means.

The cells are desirably constructed so that the metal will be contained therein while permitt-ing a free flow, of water, and so that the cells will contract under pressure as the metal is consumed during use.

Fig. 6 shows a particular desirable cell construction. A contractile enclosure of framework Silt, which may be of sponge rubber, or of flexible hollow square tubing such as rubber orsynthetic plastic, forms the periphery of the cell, Fastened by cement temporarily or permanently, or by vulcanization, to the bottom end of the framework 2% is the cloth diaphragm 234,. On two opposite sides of framework 25 are openings, and cemented across these openings are thin; rubber strips Hi2, which are perforated. The perforations allow for the ingress and egress of the water while assuring that the metal particles are contained in the cell.

In constructing a battery of cells, each cell is filled with metal particles from diaphragm 20! to the level of the upper surface of contractile framework 299. ihereupon a second similar cell is laid upon the first, in such manner that the bottom of diaphragm cloth 201 of the second cell rests upon the upper edge of framework Elli! and strips 202 of the first cell, and completely encloses the first cell. The contact with the upper edge of 206 and of 282 is sealed with cement. The seal is best of temporary, nature, so that the cells may be separated after consumption of the metal. In order to insure a temporary bond, the upper edge of framework 2% and of rubber strips 202. may firstbe protected by a cemented strip of cloth. In this way the cemented contact of diaphragm Elli of the second cell with the framework 2% and rubber stamps 202 of the first cell is made through cloth against cloth, instead of through cloth against rubber.

By thus filling each cell with sub-divided metal, and stacking one cell upon the other, a battery of cells may be formed. The terminal cells of the battery are covered with cloth, which may be pierced with the metal prick-points 2-5.

By the cell construction shown in Fig. 6, it is possible to avoid individual inlets to the cells or of punched .screens bounding the cells.

In Figs. 7 and S, the insulated tank holds the battery of cells A to E, each consisting of a diaphragm 39!, the foam rubber or hollow rubber framework 30}! bordering each cell, and the perforated strips 3&2, as shown in 6. The

battery of superposed cells provides channels 3'33 .The valve action of the end-plates M8 is maintained as the metal is consumed and while the gird-plates are moved inward by thrust screws In Fig. 6, strips 202 may desirably be slightly overlapped across the opening in framework 2613, thereby increasing the strength of the joint to cloth 20! of the cell, and to cloth 2M of the superposed cell in a battery.

While framework 26% has been shown as of hollow square rubber tubing, it may also be of U-shaped rubber or rubber-like material, the edges of which face outward from the cell. The Ushaped rubber is more collapsible than the hollow square rubber. It may also be conveniently perforated, thereby combining in one unit the functions both of framework 285 and strip 202. A portion of the perforated U-shaped rubber may be cut away, thereby furnishing the equivalent of the channel formed by framework 200 and strip 202 in Fig. 6.

It may be advantageous mechanically and hydraulically not to have the channel in the framework 200, but to provide it in tank 490.

A channel in the framework is avoided by completely overlapping strips 2% in Fig. 6, or by not cutting away the perforated U-shaped framework. In this instance, pipe itii in Fig. 8 enters a channel similar to 383 but forming a part of tank 400 beneath its lower surface; likewise, pipe 08 leads away from a channel similar to 304 but forming a part of tank 4% above its upper surface. Water entering the lower channel in tank 400 flows into each of the cells through the lower perforated strip 303 of framework 3%, which bounds each of the cells A to E laterally and on top and bottom, out through perforated strip 302 of framework 368 and into the upper channel 304 of tank iilii into pipe 498.

The desirability of substantial external pressure applied to the cells by the end-plates is shown by the results of a test, employing a canvas cloth. With tap water and aluminum turnings, and with a pressure of 15 lb. sq. ft., a current of 33 milliamps. per sq. ft. volt was obtained. When the pressure was increased to 45 lbs., the current increased to 67 milliamps. When the pressure was still further increased to 450 lbs., the current rose to 210 milliamps.

In tests of the power requirement, employing cloth diaphragms the electrical resistance of water containing electrolytes was found to be equivalent to that furnished by two metal sheet electrodes spaced from 0.05 inch to 0.10 inch apart. The diaphragm cell resistance is thus comparatively low, and a large output of metal hydroxide may be obtained with a relatively low power consumption.

As regards the hydraulic resistance to water flow, over 50% of the metal bed is free space, and the perforations of the end-strips of each cell are relatively coarse. A test was made using previously stamped aluminum turnings. With a ratio of depth of battery to square cross-sectional width of one, the pressure drop for a water flow of 50 gal. per min. per cu. ft. of battery space, was only 2 ft. of water. In usual practice, the resistance to water flow will be much less than this.

When employing the preferred series connection of the battery of cells, a gain in average current output, and a decrease in the power requirement, is obtained by periodically reversing the polarity of the terminals in Figs. 3, 4, 5 and 7. When maintaining a given polarity, a steady current through the battery of 30 milliamps. was obtained. When, however, the polarity was reversed at the rate of once in two seconds, the current was 80 to 90 milliamps. Dur- 10 ing-each reversal, the current slowly decreased during the two-second interval from 90 to 80 milliamps. The high current output on periodic reversal is apparently due to decrease of polarization of the metal in the cells.

stance of aluminum been overcome by applying voltage to the battery without reversal for a period of one or more hours. The current, after a few irregular reversals, is then found to rise to its normal value, and thereafter regular reversal of the current may be employed.

Aluminum metal, in the form generally of borings or turnings, yielded aluminum hydroxide in suspension that was capable of forming a floc with resultant clarification of turbid water. The aluminum hydroxide could be generated separately and added to the turbid water, or the latter could be passed directly through the battery, employing the embodiment of the invention in which the water flows parallel to the diaphragms. Air commingled with the water was also effective as a flushing agent for the aluminum cells.

Iron metal in the form of turnings yielded a greenish ferrous hydroxide. When air was commingled with the water, reddish brown ferric hydroxide was generated. The ferric hydroxide in suspension was effective in clarifying turbid water.

The coagulation and clarification of a turbid water by aluminum hydroxide may be promoted materially by the presence of aluminum ion, ferric ion, or hydrogen ion. The clarification by ferric hydroxide may be similarly promoted. In one instance, effective floc formation and clarification were obtained by the addition of 200 parts per million of the electrically generated aluminum hydroxide. The addition of 30 p. p. m. of the aluminum hydroxide was required for the same degree of clarification if to the water was added only 2 p. p. m. of aluminum sulfate, or 2 p. p. m. of ferric sulfate, or 8 p. p. m. of sulfuric acid. When the sulfates were added in solution form, they were effective only if their solutions were previously slightly acidified so as to have present the metal ions rather than their hydrolytic products. The ions seemed somewhat more effective if their addition followed that of the aluminum hydroxide to the turbid water.

Similar results are obtained in the instance of electrolytically generated ferric hydroxide. The addition of relatively slight amounts of aluminum ion, ferric ion, or hydrogen ion results in a relatively great reduction in the requirement of the ferric hydroxide for clarification. The magnitude of the effects is about the same as for aluminum hydroxide.

In some cases, a mixture of aluminum hydroxide and ferric hydroxide may be more effective than either alone. Electrolytically, the mixture may be obtained by mixingaluminum and iron particles in each of the cells, or by utilizing separate alternate beds of each.

Iron as an impurity in other metal chips, turnings, or borings, may be conveniently removed magnetically.

For the production of metal hydroxide for subaga n sequent use, a high rate of output was obtained by adding an electrolyte for example a 1 sodium chloride solution to the water. It is preferred generally to recirculate the solution in order to build up a satisfactory high concentration of metal hydroxide, and the latter may then be filtered and washed.

Hydroxide was generated in the instance of aluminum metal at a voltage per cell as low as /2 volt. In general, the voltage may be varied from about /2 to 20 volts, the current and hydroxide output varying in proportion.

Although the invention has been described in detail, such description is intended to be illustrative rather than limiting, as numerous embodiments will be apparent to those skilled in the art. The invention therefore is not to be limited except insofar as is necessitated by the-prior art or the spirit of the appended claims.

Having now particularly-described and ascertained the nature of the invention, and in what manner the same is to be performed, what is claimed is:

1. An electrolytic apparatus for producing metal hydroxide from sub-divided aluminum metal which comprises-an-insulating tank havin a'plurality of-compressed, independent and abutting metal beds-formed of said sub-divided'metal, water-pervious diaphragms separating the beds, a circuit to pass a current across the diaphragms and through the beds, conduit means to pass water containing electrolyte through the beds, a perforated contractile frame-work bordering each bed of metal, said frame-work being provided with an entrance and exit means connecting with said conduit, means for permitting the water to flow through the beds while restraining the divided metal in said beds, and mechanical pressure means to maintain said beds and said diaphragms under pressure transverse to the diaphragms.

2. The apparatus 'of claim 1, in which the framework includes a hollow flexible "member.

3. An electrolytic apparatus for producingmetalli'c'hydroxi'de from aseries of metal masses which'com-prisesan insulating tankga metal hydroxide producing'battery in said tank, said battery consisting of a 'pervious contractile framework divided into sections by water pervious nonconducting diaphragms forming a series of indi- 'vid'u'al and abuttin'g containers for particulate metal material, electrical means for passing a current through each of saidsections, conduit means forming inlet and outlet liquid passageway for transmission of liquids-through said battery and liquid by-pass conduit means including pump means associated with said tankto recirculate a, portion of thebattery liquid passing'from the outlet side of said battery'back into "the inlet side of said battery.

4. Anelectrolytic method of'pro'ducing'm'etal hydroxide in susp'ension'in an electrolyte from a metal mass formed into a plurality of electrode beds by water pervious, *non co'nducting "diaphragms and a bordering framework whichcomprises passing an electric current a'crossthe'diaphragms and through the -metal mass'of the several beds, simultaneously passing "electrolyte through the metal mass, recirculating electrolyte containing metal hydroxide back through the said metal mass, and maintaining'the' passage of electric current through the said metal'mass, thereby increasing'theyield ofmetal hydroxide in suspension in the electrolyte.

'5. An "electrolyticmethod'of producing metal 1-2 hydroxide in suspension in an electrolyte from a metal mass formed into a plurality of beds "by water-pervious, non-conducting diaphragms and a-contractile framework, whichcomprises passing an electric current across the diaphragms and through the metal mass of the severalbeds while passing electrolyte through the metalmass, and mechanically maintaining a continuously compacting and compressing pressure on the beds ofmetal normal to the diaphragms. V

6. An electrolytic method of producing metal hydroxide in suspension in an electrolyte from subdivided metal particles wherein the particles are contained in a plurality of separate, independent and abutting beds separated by porous non-conducting diaphragms, the beds being laterally bounded by a contractile framework pervious to an electrolyte, which comprises passing an electric current across the diaphragms and through'the metal masses of the'beds, andsi'mul- 'taneously passing electrolyte across the contrac "tile framework into and through the metal masses of the beds in a direction-transverse to the fiow of the electric current.

7. An electrolytic method of producing metal hydroxide in suspension in an electrolyte from subdivided'metal particles wherein the particles are contained in a plurality of separate, independent and abutting beds separated by porous, non-conductive diaphragms, the bedsbe'ing lat- "erally bounded bya flexible framework pervious to an electrolyte, whichcomprises compressing and compacting the plurality of beds by the continuous application of mechanical pressure to the flexible framework, passing an electric current across the diaphragms 'and through the metal masses-of the beds, *and simultaneously passing electrolyte across the flexible-framework into and throughthe metal masses of thc beds in a direotion-transverse-to the flow'of the electric current. i

8. Ari-electrolytic method of-producing metal hydroxide 'in suspension in anelectrolyte from subdivided metal particles wherein the particles are contained in a plurality of "separate, independent and "abutting bedsseparated by'porous, non-conductive diaphragms, the bedsbcing laterally bounded by a flexible framework "pervio'u-s 'to an electrolyte, which-comprisescompressing and compacting the plurality of beds by *the "continuous application of mechanical pressure "to the flexible framework, passing an electric current'across the diaphragms and'through the metal masses of the beds, simultaneouslypa ssing electrolyte across the flexible framework into and through the'metal masses of the'beds in direction transverse to the flow of the electric current, and recirculating a portion of -the efliu ent product obtained I from the-reaction of the metal particles and'electrolyteunder the influence of the electric current into the electrolyte passing into'the metal-massesof the beds.

9. Ari-electrolytic apparatus for producing a concentrated solution of metal-hydroxide from a series of metal masses which comprises an insulating tank, -a -metal hydroxide-producing battery in said tank, said battery consisting 0i flexible bordering'frameworks and porous nonconducting diaphragms forming series'of individual'and abutting contractile containers-fer said metal masses, electrical means for passing a current through each ofsaidsecti'ons, and inlet and outlet liquid conduit means on saidtank for transmitting and recirculating metal hydroxideefiiuent through saidcontainers.

10. An electrolytic apparatus for producing a concentrated solution of metal hydroxide from a series of metal masses which comprises an insulating tank, a metal hydroxide-producing battery in said tank, said battery consisting of flexible bordering frameworks and porous non-conducting diaphragms forming a series of individual and abutting contractile containers for said metal masses, electrical means for passing a current through each of said sections, inlet and outlet liquid conduit means on said tank for transmitting and recirculating metal hydroxide effiuent through said containers, and mechanical means for maintaining said framework and diaphragms under transverse pressure.

11. An electrolytic apparatus for producing metallic hydroxide from a series of metal masses which comprises an insulating tank, a metal hydroxide producing battery in said tank, said battery consisting of a pervious contractile framework divided into sections by water pervious non-conducting diaphragms forming a series of individual and abutting containers for particulate metal material, electrical means for passing a current through each of said sections, conduit means forming inlet and outlet liquid passageway for transmission of liquids through said battery, liquid by-pass conduit means including pump means associated with said tank to recirculate a portion of the battery liquid passing from the outlet side of said battery back into the inlet side of said battery, and mechanical means for maintaining said sections and said framework under pressure transverse to said separator means.

12. An apparatus for electrolytic production of metal hydroxide from sub-divided aluminum metal which comprises a tank having insulating interior wall surfaces, a battery formed of a plurality of independent beds containing said subdivided compacted compressed aluminum therein, water-pervious non-conducting flexible diaphragms between the beds, a perforated contractile framework bordering each bed permitting passage of water containing an electrolyte therethrough and preventing passage of metal particles, a conduit and valve arrangement to pass the water through the beds, and recirculating pump and conduit means associated with said battery for returning water containing aluminum hydroxide thereto to increase the yield of aluminum hydroxide in the battery water.

13. The method of producing metal hydroxide in suspension in an electrolyte which comprises passing an electric current across a battery of electrodes of a metal capable of generating the corresponding metal hydroxide, simultaneously passing the electrolye over the electrodes to generate metal hydroxide therein, passing the electrolyte containing the freshly generated metal hydroxide from said battery of electrodes, and upon passage of the said electrolyte containing freshly generated metal hydroxide from said battery of electrodes, without separation of the metal hydroxide content thereof, recirculating electrolyte containing said initially produced freshly generated, unseparated, suspended and non-settled metal hydroxide back through the battery of electrodes, while current is being passed through said electrodes, thereby producing a relatively increased yield of dispersed metal hydroxide in suspension.

14. An electrolytic apparatus for producing an increased yield of dispersed and uncoagulated metal hydroxide in suspension in an electrolyte efiluent comprising an insulating tank, fluid inlet and outlet conduit means connected to said tank, a battery of electrodes of a metal capable of generating the corresponding metal hydroxide in said tank, electrical means for passing a current through said battery, and'a battery effluent recirculating pump and conduit directly connected between said fluid inlet and outlet conduit means for a direct return of freshly generated metal hydroxide efliuent to said battery without an intermediate separation chamber between said return conduit and said battery, whereby the eiiiuent is recirculated without separation of its freshly generated metal hydroxide content directly back past said metal hydroxideproducing electrodes.

15. An electrolytic apparatus for producing an increased yield of dispersed metal hydroxide in suspension in an electrolyte comprising a battery having an inflow side and an outflow side, of a metal capable of generating the corresponding electrodes in said battery metal hydroxide, fluid inlet and fluid outlet conduits for said battery, bypass conduits interconnecting the outflow battery side with the inflow battery side without an intermediate separation chamber therein, and a recirculating pump in said by-pass for pumping electrolyte and freshly generated metal hydroxide as it passes from said outlet side of said battery directly back through said inlet side into said battery without separation of the said freshly generated metal hydroxide contained in the said electrolyte passing back into said battery, whereby metal hydroxide as it is produced in an electrolyte in said battery is recirculated from the said outflow side of said battery to the inflow side of said battery in a return flow past said metal electrodes.

16. An electrolytic battery for producing an improved yield of dispersed aluminum hydroxide in suspension comprising a battery case having a water inlet side and a water outlet side, water conduit means associated with said battery case, aluminum electrodes in said battery case, electric conductors connected to said electrodes, a fluid by-pass conduit passing from the water outlet side directly to the Water inlet side of said battery case without an intermediate separation chamber, and water circulation forcing means in said by-pass for recirculating water containing suspended and non-settled electrolytically produced dispersed metal hydroxide passing from the said outlet side of said battery to the said inlet side of said battery and back through said battery case without intermediate separation and at an increased flow rate, whereby an improved yield of dispersed aluminum hydroxide is produced in the water passing through said battery.

17. The method of producing an improved yield of metal hydroxide in suspension in water comprising passing an electric current into a battery of electrodes of a metal capable of generating the corresponding metal hydroxide, simultaneously passing water over the said electrodes, and simultaneously and continuously without separation of the freshly generated metal hydroxide content recirculating a portion of the water containing freshly generated, suspended and nonsettled metal hydroxide back through the said electrodes during passing of said electric current thereto, thereby increasing the yield of dispersed and uncoagulated metal hydroxide in the water passing over the said electrodes.

PAUL S. ROLLER.

(References on following page) mama-e References Cited in the file: ofl patent. UNITED STATES PATENTS Number Name Date.- Frazer July, 30, 1895 Harris r Qet, 19.; 190,9. Hartman Mar. 8, 1910 Smith July: 1,, 19241: Smith Noy. 11,,1-924, Speed 1 O.ct.., 19, 19.261 Kean Jan. 5,.1-932 Kuhl Oct 1-8, 1938 Number Number Name; Date Andrus Mar; 26, 1940 FOREIGN PATENTS Country Date France Jan. 12, 1903 France Apr. 28, 1931 Germany May 13, 1922 Great Britain July 15, 1935 Great-Britain Oct. 27, 1942 

13. THE METHOD OF PRODUCING METAL HYDROXIDE IN SUSPENSION IN AN ELECTROLYTE WHICH COMPRIES PASSING AN ELECTRIC CURRENT ACROSS A BATTERY OF ELECTRODES OF A METAL CAPABLE OF GENERATING THE CORESPONDING METAL HYDROXIDE, SIMULTANEOUSLY PASISNG THE ELECTROLYE OVER THE ELECTRODES TO GENERATE METAL HYDROXIDE THEREIN, PASSING THE ELECTROLYTE CONTAINING THE FRESHLY GENERATED METAL HYDROXIDE FROM SAID BATTERY OF ELECTRODES, AND UPON PASSAGE OF THE SAID ELECTROLYTE CONTAINING FRESHLY GENERATED METAL HYDROXIDE FROM SAID BATTERY OF ELECTRODES, WITHOUT SEPARATION OF THE METAL HYDROXIDE CONTENT THEREOF, RECIRCULATING ELECTROLYTE CONTAINING SAID INITIALLY PRODUCED FRESHLY GENERATED, UNSEPARATED, SUSPENDED AND NON-SETTLED METAL HYDROXIDE BACK THROUGH THE BATTERY OF ELECTRODES, WHILE CURRENT IS BEING PASSED THROUGH SAID ELECTRODES, THEREBY PRODUCING A RELATIVELY INCREASED YIELD OF DISPERSED METAL HYDROXIDE IN SUSPENSION. 